Topological Kondo Insulator from Spin Loop Currents

TL;DR

This paper predicts and explains the emergence of a topological Kondo insulator in AB-stacked MoTe2/WSe2 bilayers, driven by non-local interactions and quantum geometry effects, aligning with recent experimental observations.

Contribution

It introduces a mechanism where non-local interactions induce spin loop currents that open a gap, leading to a topological Kondo insulator in moiré materials.

Findings

Non-local interactions enable spin loop currents that open a full gap.

The topological Kondo insulator appears at intermediate displacement fields.

Results align with experiments showing phase transitions controlled by displacement field.

Abstract

We demonstrate that interacting electrons in AB-stacked $\mathrm{MoTe}_2/\mathrm{WSe}_2$ realize a topological Kondo insulator at hole filling $\nu=2$ per moir\'e unit cell. In the presence of only local correlations, a symmetry of the moir\'e-scale bandstructure enforces a compensated topological semimetal by tying band inversion to band overlap. We show that non-local interactions change the physics qualitatively, since they allow intrinsic, quantum-geometry-induced spin loop currents to feed back on the effective bandstructure, which lift the remaining accidental degeneracies and open a full gap in the spectrum, leading to a fully gapped topological Kondo insulator. We establish this using real-frequency dynamical mean-field theory to capture Kondo physics alongside Hartree-Fock for non-local interactions. The topological Kondo insulator emerges at intermediate displacement fields, where strong correlations manifest through an enhanced spin susceptibility, a suppressed charge susceptibility, and a stronger thermal dependence of the resistivity. Our results are in good agreement with recent experiments on $\mathrm{MoTe}_2/\mathrm{WSe}_2$ bilayers demonstrating topological to trivial phase transitions controlled by the displacement field.